Conventionally, as a cutting insert (hereinafter referred to as an “insert” in some cases) used for performing a face milling process, an insert whose both hexagonal shaped surfaces are usable has been proposed (for example, refer to International Publication No. 2007/037733).
According to the insert of the International Publication No. 2007/037733, a flat surface is formed on an upper surface as shown in FIGS. 1A and 1E thereof. The flat surface functions as a mount surface brought into contact with an insert pocket when a cutting edge located closer to a lower surface is used.
The above insert is generally obtained by subjecting raw material powder to press molding and firing. However, deformation may occur during the firing due to shape factor and firing environmental variations or the like. For example, even when the surface functioning as the mount surface is molded flat, the deformation may occur by the firing. Consequently, the mount surface of the insert is brought into contact with a position different from an intentional position at a design stage, and thus there is a risk of deterioration of attachment stability.